1). Field of the Invention
This invention relates generally to an electronic assembly and more specifically to the manner in which power, ground, and signals are provided to integrated circuits of the electronic assembly.
2). Discussion of Related Art
Integrated circuits are formed on semiconductor wafers. The wafers are then sawed into microelectronic dies, also known as semiconductor chips. Each semiconductor chip is then mounted to a package, or carrier, substrate. Often the packages are then mounted to a motherboard.
The integrated circuit receives power, ground, and other electronic signals through contacts located between the semiconductor chip and the carrier substrate and vias in the package substrate. The vias extend from an upper surface to a lower surface of the carrier substrate and pass through a core made of an organic material. In order to send an electronic signal from one semiconductor chip to another, the signal must first pass from one of the semiconductor chips down through a via in the substrate, laterally across the motherboard, and back up through another via connected to the other semiconductor chip.
The use of vias for power, ground, and signal conductors at the same time is unsuitable for the power requirements of state of the art microelectronic applications. Because of high loop inductance of the system, three voltage drops, also known as first, second, and third xe2x80x9cdroops,xe2x80x9d occur at different times during use. A number of decoupling capacitors must be used, increasing the cost of the assembly. The signal integrity of signals sent between the semiconductor chips is weakened due impedance mismatches between the different substrates. The resistance encountered by the current used for power the chips is unnecessarily high because not all of the vias are used for power so that the power delivered to the semiconductor chips is not maximized. The organic core does not have a good coefficient of thermal expansion, and for mechanical support, it must be made thicker which adds inductance and increases the first droop.